Porthole Retrofit Apparatus for a Monopole Tower

ABSTRACT

An apparatus for the flameless retrofit of a monopole tower with additional portholes is presented. The apparatus includes a frame, a front plate, a back plate, and a plurality of fasteners. The frame has a through hole which defines a porthole allowing access to the interior of the monopole. The front plate has an opening which fits about the frame and is contoured to match the exterior surface of the monopole. The back plate has an opening shaped which fits about the frame. The back plate is fixed to the frame so that the frame extends from both sides of the back plate and through a crude opening cut into the monopole. The back plate is contoured to match the interior surface along the monopole. The front and back plates are disposed about the crude opening and attached to the monopole via the fasteners. Each fastener passes through holes mutually aligned along each of the front plate, monopole, and back plate. The apparatus and mechanical fastening means ensure the structural integrity of a monopole tower and completely avoid the need for welding methods during assembly onto the monopole.

CROSS REFERENCE TO RELATED APPLICATIONS

None.

FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

None.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to the field of monopole towers. Inparticular, the invention is an apparatus which is mechanically fastenedabout a rough opening cut into a wall of a monopole tower so as toprovide a porthole facilitating the passage of cables into and out ofthe tower. The apparatus and mechanical fastening means ensure thestructural integrity of the tower and completely avoid the use ofwelding methods which are a primary cause of fires within monopoletowers.

2. Background

A monopole tower is a cylindrically-shaped, hollow structure, typicallycomposed of steel, fixed at its lower end to a foundation and having asupport structure at its upper end. Monopole towers are used by thetelecommunications industry within cell sites to form a cellulartelephone network.

A cell site usually includes at least one monopole tower, two or moreantennas, and other electronic equipment. Antennas are placed onto thesupport structure at the top of the monopole tower. Transmitters,receivers, transceivers, digital signal processors, control electronics,GPS receivers, and power sources are provided within a shelter immediateadjacent to the base of the tower. Cables are provided within theinterior of the monopole between the antennas at the top of the towerand equipment within the shelter at the base of the tower.

The expansion of antenna capacity at the top of a monopole could requirethe addition of new openings at one or both ends of a tower. Theaddition of a new opening along a monopole tower requires a skilledwelder to cut a crude opening into the wall structure of a tower. Atypical crude opening includes irregular edges which cut or otherwisedamage cables entering and exiting the tower. A porthole apparatus issecured about the hole and then welded onto the monopole structure to asto provide a smooth and uniform opening through which cables passwithout damage. The welding process produces molten metal whichinvariably falls into the hollow center of the monopole often initiatinga fire. Such fires are particularly difficult to extinguish due to thestack effect.

The stack effect is the movement of air caused by buoyancy into and outof a vertically-disposed, hollow structure, such as a monopole tower. Apositive or upward buoyancy results when hot, less-dense air is producedwithin a monopole surrounded by cooler, more-dense air. The greater thethermal difference between internal and external conditions and thetaller the structure, the greater the buoyancy force and stack effect.The stack effect enables a fire at the base of a monopole tower toquickly progress up along the length of the tower, thus consuming cableswithin the tower and damaging antennas at the top of the tower.Furthermore, heat generated within the tower is often sufficient to meltor weaken the structure causing it to bend and/or collapse.

Coberly, U.S. Pat. No. 7,234,276, describes a porthole apparatus havinga rectangular frame with a planar-shaped bar disposed about theperiphery of the frame. The rectangular frame traverses a crude openingwithin the monopole so that the bar contacts the interior surface of themonopole. The rectangular frame and bar are then welded onto the tower.The weld specifications for monopole towers require welds to traversethe wall thickness of the pole so as to avoid a mechanical weakening ofthe tower. Accordingly, the design and method described by Coberly areunable to prevent molten metal from falling into the center cavity of atower so as to avoid the possibility of a fire therein.

As is readily apparent from the discussions above, the related arts donot provide an apparatus for use about a crude opening along a monopoletower which avoids the fire hazards associated with welding whilemaintaining the structural integrity of the tower.

Therefore, what is required is a frame apparatus which is mechanicallyattachable to a monopole structure about a crude opening so as to avoidthe fire hazard associated with welding, to minimize the structuralimpact of the crude opening along the tower, and to provide a portthrough which cables enter and exit the tower without damage.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a frame apparatus whichis mechanically attachable to a monopole structure about a crude openingso as to avoid the fire hazard associated with welding, to minimize thestructural impact of the crude opening along the tower, and to provide aport through which cables enter and exit the tower without damage.

Various embodiments of the apparatus include a frame, a front plate, aback plate, and a plurality of fasteners. The center open portion of theframe forms the porthole. The front plate has an opening which fitsabout the frame and is contoured to match the exterior surface of thetower. The back plate has an opening shaped so as to also fit about theframe. The back plate is fixed to the frame so that the frame extendsfrom both sides of the back plate and through the crude opening cut intoa side of a monopole tower. The back plate is contoured to match theinterior surface along the tower. The front and back plates are disposedabout the crude opening and attached to the wall via the fasteners. Eachfastener passes through holes mutually aligned along each of the frontplate, back plate, and tower.

Several advantages are offered by the invention. The invention avoidsonsite welding, thus avoiding a primary cause of fires within monopoletowers. The invention is customizable for a variety of monopole designs.The invention eliminates pre-heating of a monopole during cold weatherinstallations. The invention maximizes antenna capacity of a monopoletower while minimizing attachment of cables along the exterior of thetower.

REFERENCE NUMERALS 1 Apparatus 2 Frame 3 Front plate 4 Back plate 5Fastener 6 Porthole 7 Weld seam 8 Width 9 Length 10 Height 11 Opening 12Monopole 13 Wall 14 Interior surface 15 Exterior surface 16 Bend 17 Bolt18 Washer 19 Lock washer 20 Nut 21 Interlayer 22 Interlayer 23 Opening24 Opening 25 Opening 26 Opening 27 Opening 28 Interior 29 Exterior 30Opening 31 Front surface 32 Back surface 33 Thickness 34 Crude opening35 Thickness

BRIEF DESCRIPTION OF THE INVENTION

Additional aspects, features, and advantages of the invention will beunderstood and will become more readily apparent when the invention isconsidered in the light of the following description made in conjunctionwith the accompanying drawings.

FIG. 1 is a perspective view illustrating the apparatus including aframe with porthole, front plate, back plate, and a plurality offasteners in accordance with an embodiment of the invention.

FIG. 2 is a front view illustrating attachment of a front plate about acentral frame with porthole via a plurality of fasteners in accordancewith an embodiment of the invention.

FIG. 3 is a back view illustrating attachment of a back plate about acentral frame with porthole in accordance with an embodiment of theinvention.

FIG. 4 is an exploded section view illustrating attachment of a backplate about a central frame with porthole via a weld seam and placementof a front plate about the frame in accordance with an embodiment of theinvention.

FIG. 5 is a partial section view illustrating attachment of an apparatusalong three side walls of a twelve-sided monopole in accordance with anembodiment of the invention.

FIG. 6 is an enlarged partial section view illustrating arrangement of afastener through a front plate, side wall, and back plate in accordancewith an embodiment of the invention.

FIG. 7 is an enlarged partial section view illustrating arrangement of afastener through a front plate, optional interlayer, side wall, optionalinterlayer, and back plate in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to several preferred embodiments ofthe invention that are illustrated in the accompanying drawings.Wherever possible, same or similar reference numerals are used in thedrawings and the description to refer to the same or like parts. Thedrawings are not to precise scale.

Referring now to FIGS. 1-3, the apparatus 1 includes a frame 2 which isshaped so as to form a porthole 6 and extends in a generally horizontalarrangement. The frame 2 could be composed a several planar-shaped orarcuate-shaped plates which are welded or otherwise joined to form asingle structure. For example, FIGS. 1-3 show a four-sided frame 2composed of four planar-shaped elements. The frame 2 could likewiseinclude a single circular-shaped element, two or more arcuate-shapedelements, or three or more planar elements. It is also possible for theframe 2 to include both arcuate and generally linear elements providingan infinite variety of opening configurations for the porthole 6.

A front plate 3 and a back plate 4 are disposed about the frame 2 in asubstantially perpendicular arrangement. The front plate 3 is a shapedelement having an opening 11 which closely approximates the outerperimeter of the frame 2. For example, FIG. 2 shows the front plate 3disposed about the frame 2 so that the dimensions of the opening 11 areslightly larger than the width 8 and length 9 of the rectangular-shapedframe 2. The back plate 4 is likewise a shaped element having an opening30 which closely approximates the outer perimeter of the frame 2. Forexample, FIG. 3 shows the back plate 4 disposed about the frame 2 sothat the dimensions of the opening 30 are slightly larger than the width8 and length 9 of the rectangular-shaped frame 2. In preferredembodiments, the front plate 3 and back plate 4 should freely slidealong the frame 2 without binding. The openings 11, 30 are cut into thefront plate 3 and back plate 4, respectively, via methods understood inthe art. The lateral dimensions and thickness of the front plate 3 andback plate 4 are design dependent, and based in part on the size theporthole 6 and load requirements imposed by the modified monopole tower.In preferred embodiments, the lateral dimensions for the front plate 3and back plate 4 are approximately the same.

The front plate 3 and back plate 4 are mechanically fastened to eachother via a plurality of fasteners 5. The fasteners 5 are disposedadjacent to the outer edge of the front plate 3 and back plate 4 and therespective openings 11, 30. The location and number of fasteners 5 aredesign dependent and determined in part by the stress field within themonopole structure adjacent to the apparatus 1.

In preferred embodiments, the front plate 3, back plate 4, frame 2, andfasteners 5 could be composed of a metal coated with a rust inhibitor,one example being zinc, and having at least the mechanical strength ofthe material comprising the monopole. In other embodiments, the frontplate 3, back plate 4, frame 2, and/or fasteners 5 could be composed ofa non-metallic composite with or without fiber reinforcement or otherhigh-strength, low-weight material.

Referring now to FIG. 4, the frame 2 is disposed within the opening 30along the back plate 4 with a height 10 so that a portion of the frame 2extends beyond the front surface 31 and the back surface 32 of the backplate 4. In preferred embodiments, the length of extension beyond thefront surface 31 should be greater than that beyond the back surface 32so as to accommodate the thickness 33 of the wall 13 comprising themonopole 12, as represented in FIGS. 4 and 5, and the thickness 35 ofthe front plate 3 with or without angular adjustments, and further toallow a portion of the frame 2 to extend beyond the front plate 3. Theframe 2 is fixed or otherwise attached to the edges of the opening 30along the back plate 4 via a weld seam 7. The back plate 4 is welded tothe frame 2 prior to installation onto a monopole 12.

The front plate 3 is separately movable within the exterior 29 withrespect to the sub-assembly formed by the frame 2 and back plate 4. Thefront plate 3 is placed over the frame 2 so that the opening 11surrounds the frame 2. Alignment of the openings 11, 30 about the frame2 ensures an unobstructed porthole 6 enabling the passage of one or morecables between the interior 28 and exterior 29.

In preferred embodiments, the frame 2 could closely approximate thegeneral shape of the crude opening 34 cut into the monopole 12. Theframe 2 should be dimensionally smaller than the crude opening 34 so asto allow the frame 2 to be freely insertable into the crude opening 34from the interior 28 of the monopole 12, as represented in FIG. 4.

The crude opening 34 is cut into the monopole 12 using a flamelessdevice and/or method in order to avoid the introduction of hot or moltenmetal into the center of the monopole 12. Exemplary flameless devicesinclude, but are not limited to, a saw with diamond tip cutting blade, awater jet, and a laser. The frame 2 covers the otherwise jagged orirregular shaped crude opening 34.

Referring now to FIG. 5, the apparatus 1 is shown attached to a portionof a monopole 12 having a cross section comprised of twelve generallyplanar walls 13. It is important to note that the apparatus 1 isapplicable to a variety of monopole 12 designs, including configurationshaving more or less than twelve planar-shaped walls 13, as well ascircular and other shaped walls 13.

The apparatus 1 is attached to the monopole 12 so that the back plate 4contacts the interior surface 14 and the front plate 3 contacts theexterior surface 15 of two or more walls 13 comprising the monopole 12.This arrangement places the front plate 3 along the exterior 29 and theback plate 4 within the interior 28 of the monopole 12. The angularcontour of the monopole 12 is replicated along the front plate 3 andback plate 4 by bends 16 disposed in a symmetrical arrangement about theframe 2. In preferred embodiments, the front plate 3 and back plate 4should contact the respective exterior and interior surfaces 15, 14along the monopole 12. In other embodiments, the front plate 3 and backplate 4 could include three or more bends 16 or a curved or arcuateprofile.

A plurality of fasteners 5 are used to secure the front plate 3 to theback plate 4 and frame 2. This arrangement ensures the apparatus 1 issecured to the walls 13 via compression of the walls 13 between thefront plate 3 and the back plate 4.

Referring now to FIG. 6, an exemplary fastener 5 is shown including abolt 17, a washer 18, a lock washer 19, and a nut 20. However, otherhigh-strength fasteners 5 are likewise applicable. The front plate 3,wall 13, and back plate 4 each include an opening 23, 24, and 25,respectively, which align to allow the passage of the bolt 17 withoutbinding. Openings 23-25 could be mechanically drilled into the frontplate 3, wall 13, and back plate 4 either during fabrication of theapparatus 1 or during installation of the apparatus 1 onto a monopole12.

In preferred embodiments, the bolt 17 is positioned perpendicular to theplane of the front plate 3 and back plate 4 immediately surrounding thebolt 17. The washer 18 and lock washer 19 are separately disposed aboutthe front plate 3, wall 13, and back plate 4, as represented in FIG. 6,so as to be perpendicular to the centerline of the bolt 17. The nut 20is threaded onto the bolt 17 and tightened so as to apply a compressiveforce onto the front plate 3 and back plate 4, and thereafter onto thewall 13.

In some embodiments, it might be advantageous to include an interlayer21, 22 between the front plate 3 and wall 13 and/or between the backplate 4 and wall 13, as shown in FIG. 7. The interlayers 21, 22 couldcompletely or partially surround the frame 2 or reside immediatelyadjacent to and surround each fastener 5. The interlayers 21, 22 couldbe a composition that is applied in flowable form, much like a paint ora caulk, or solid form, examples including but not limited to a film,gasket, or plate-shaped element, between the respective elements.

The front plate 3, interlayer 21, wall 13, interlayer 22, and back plate4 each include an opening 23, 26, 24, 27, and 25, respectively, whichalign to allow the passage of the bolt 17 without binding. Openings23-27 could be mechanically drilled into the respective elements eitherduring fabrication of the apparatus 1 or during installation of theapparatus 1 onto a monopole 12. When the interlayer 21, 22 is applied ina flowable form, the opening 26, 27 through each interlayer 21, 22 couldbe formed by masking the applicable surface. In some embodiments, theinterlayers 21, 22 could extend into the respective openings 23, 25along the front plate 3 and back plate 4. In other embodiments, theinterlayers 21, 22 could extend into the respective openings 23, 25along and cover the respective front plate 3 and back plate 4immediately adjacent to contact surface with the lock washer 19 andwasher 18.

In one example, the interlayers 21, 22 could be an adhesive whichresides along one surface of the front plate 3 and back plate 4 andimmediately contacts the exterior surface 15 and interior surface 14 ofthe walls 13, respectively. The adhesive could temporarily hold thefront plate 3 and back plate 4 onto the monopole 12 during assembly ofthe apparatus 1 onto the monopole 12.

In other embodiments, the interlayers 21, 22 could provide a thermal orelectrical barrier or short circuit between the monopole 12 and thefront plate 3, back plate 4, and/or fastener 5. The interlayers 21, 22could be composed of materials including, but not limited to, acompressible or non-compressible polymer, elastomer, or rubbercomposition. These embodiments might also require the fasteners 5 to becomposed of or coated with a thermally or electrically non-conductivematerial.

In yet other embodiments, the interlayers 21, 22 could provide a fluidbarrier which prevents water or air infiltration along the exterior 29into the interior 28 of the monopole 12. The interlayers 21, 22 could becomposed of materials including, but not limited to, a compressible ornon-compressible polymer, elastomer, or rubber composition. Thisarrangement would be beneficial when the interior 28 of the monopole 12is sealed from the outside environment.

The description above indicates that a great degree of flexibility isoffered in terms of the invention. Although various embodiments havebeen described in considerable detail with reference to certainpreferred versions thereof, other versions are possible. Therefore, thespirit and scope of the appended claims should not be limited to thedescription of the preferred versions contained herein.

What is claimed is:
 1. An apparatus for retrofitting a porthole along amonopole tower comprising: (a) a frame having a first opening whichdefines said porthole; (b) a front plate having a second opening shapedso as to fit about said frame, said front plate contoured to match anexterior surface along said monopole tower; (c) a back plate having athird opening shaped so as to fit about said frame, said back platefixed to said frame so that said frame extends from both sides of saidback plate and through a crude opening along said monopole tower, saidback plate contoured to match an interior surface along said monopoletower; and (d) a plurality of fasteners; where said front plate and saidback plate are disposed about said crude opening and attached to saidmonopole tower via said plurality of fasteners, each said fastenerpassing through holes mutually aligned along each of said front plate,said monopole tower, and said back plate.
 2. The apparatus of claim 1,wherein said front plate and said back plate include at least one bendor curve matching the contour of said monopole tower.
 3. The apparatusof claim 1, wherein said back plate is fixed to said frame via weldingprior to installation onto said monopole tower.
 4. The apparatus ofclaim 1, further comprising: (e) at least one interlayer disposedbetween said front plate and said monopole tower and/or said back plateand said monopole tower.
 5. The apparatus of claim 4, wherein said atleast one interlayer is an adhesive.
 6. The apparatus of claim 4,wherein said at least one interlayer provides an electrical shortcircuit between said monopole tower and said front plate, said backplate, said frame, and/or said plurality of fasteners.
 7. The apparatusof claim 4, wherein said at least one interlayer provides a thermalshort circuit between said monopole tower and said front plate, saidback plate, said frame, and/or said plurality of fasteners.
 8. Theapparatus of claim 4, wherein said at least one interlayer provides afluid barrier between said monopole tower and said front plate, saidback plate, said frame, and/or said plurality of fasteners.
 9. Theapparatus of claim 1, wherein said crude opening is cut into saidmonopole tower via a mechanical device, a water jet, or a laser.
 10. Theapparatus of claim 1, wherein said front plate, said back plate, saidframe, and/or said plurality of fasteners are comprised of anon-metallic composite with or without fiber reinforcement.
 11. A methodof retrofitting a porthole along a monopole tower comprising the stepsof: (a) cutting a crude opening into said monopole tower via a flamelessmethod; (b) inserting a frame into said crude opening, said frame havinga first opening which defines said porthole, a back plate disposed aboutand fixed to said frame so that said frame extends from said back platein two directions, said back plate bent and/or curved so as to contactand match an interior surface along said monopole; (c) placing a frontplate onto said frame, said front plate having a third opening so as tofit about said frame, said front plate bent and/or curved so as tocontact and match an exterior surface along said monopole tower; and (d)compressing said monopole tower between said front plate and said secondplate via a plurality of fasteners.
 12. The method of claim 11, whereinsaid flameless method is performed via a mechanical device, a water jet,or a laser.
 13. The method of claim 11, further comprising the step of:(e) including an interlayer between said back plate and said monopoleand/or said front plate and said monopole.
 14. The method of claim 13,wherein said interlayer provides a thermal short circuit between saidmonopole tower and said front plate, said back plate, said frame, and/orsaid plurality of fasteners.
 15. The method of claim 13, wherein saidinterlayer provides an electrical short circuit between said monopoletower and said front plate, said back plate, said frame, and/or saidplurality of fasteners.
 16. The method of claim 13, wherein saidinterlayer provides a fluid barrier between said monopole tower and saidfront plate, said back plate, said frame, and/or said plurality offasteners.